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Emerging SARS-CoV-2 variants have made COVID-19 convalescents susceptible to re-infection and have raised concern about the efficacy of inactivated vaccination in neutralization against emerging variants and antigen-specific B cell response. To this end, a study on a long-term cohort of 208 participants who have recovered from COVID-19 was conducted, and the participants were followed up at 3.3 (Visit 1), 9.2 (Visit 2), and 18.5 (Visit 3) months after SARS-CoV-2 infection. They were classified into three groups (no-vaccination (n = 54), one-dose (n = 62), and two-dose (n = 92) groups) on the basis of the administration of inactivated vaccination. The neutralizing antibody (NAb) titers against the wild-type virus continued to decrease in the no-vaccination group, but they rose significantly in the one-dose and two-dose groups, with the highest NAb titers being observed in the two-dose group at Visit 3. The NAb titers against the Delta variant for the no-vaccination, one-dose, and two-dose groups decreased by 3.3, 1.9, and 2.3 folds relative to the wild-type virus, respectively, and those against the Omicron variant decreased by 7.0, 4.0, and 3.8 folds, respectively. Similarly, the responses of SARS-CoV-2 RBD-specific B cells and memory B cells were boosted by the second vaccine dose. Results showed that the convalescents benefited from the administration of the inactivated vaccine (one or two doses), which enhanced neutralization against highly mutated SARS-CoV-2 variants and memory B cell responses. Two doses of inactivated vaccine among COVID-19 convalescents are therefore recommended for the prevention of the COVID-19 pandemic, and vaccination guidelines and policies need to be updated.
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So far,the coronavirus disease 2019(COVID-19)has been persisting for nearly three years,infecting about 700 million people and causing more than 6 million deaths,which has seriously affected the human society.According to Global Initiative on Sharing All Influenza Data,there are more than 12 million SARS-CoV-2 variants,of which the five major variants of concern are Alpha,Beta,Gamma,Delta and Omicron.Their infectivity,pathogencity,and neutralization resistance have changed greatly compared with the original strain,which has brought great pressure to the prevention and control of the pandemic.Antibody level testing is critical for confirming infection,epidemiological investigation,vaccine development,and neutralizing drug preparation.Focusing on the humoral immunity against SARS-CoV-2,this paper introduces the mutation sites,neutralization resistance,and vaccination efficacy of the five variants of concern,and briefly summarizes the evolutionary characteristics,future mutation directions,and host immunity.
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Humans , SARS-CoV-2/genetics , Antibody Formation , COVID-19 , Gamma Rays , Antibodies, Neutralizing , Antibodies, ViralABSTRACT
@#Objective To prepare high titer specific immune serum of varicella-herpes zoster virus(VZV)for the quality control of live attenuated varicella vaccine and live attenuated herpes zoster vaccine.MethodsMale rabbits were immunized with high purity recombinant gE glycoprotein combined with Freund's adjuvant,aluminum hydroxide adjuvant or MF59 adjuvant,2 rabbits in each group. On the 56th day after immunization,the maximum blood samples(heart or carotid artery)were collected from each rabbit to prepare serum,which was mixed with VZV for neutralization reaction,and then inoculated into a 6-well plate full of monolayer of MRC-5 human diploid cells. After incubation for 7 d,the number of plaques was counted and the neutralizing titer and virus neutralizing ability of immune serumwere determined. The serum with high neutralizing titer and virus neutralizing ability was selected for the identification test of live attenuated varicella vaccine and live attenuated herpes zoster vaccine VZV(Oka strain)working seed lot and the detection of exogenous virus factors.ResultsThe immune sera prepared by immunizing rabbits with various combinations of recombinant gE glycoprotein all showed neutralizing activity,among which the serum prepared by the combination of recombinant gE glycoprotein and Freund's adjuvant had the highest neutralizing titer of 1∶512 and the virus neutralizing ability of 240 000 PFU/mL;The prepared immune serum was usedfor the identification test of VZV(Oka strain)working seed lot and the detection of exogenous virus factors,of which all the results were in line with the requirements. Conclusion The recombinantgE glycoprotein could be used for the preparation of high titer neutralizing antibody against VZV,and the prepared high titer neutralizing antibody is suitable for thequality control of live attenuated varicella vaccine and live attenuated herpes zoster vaccine.
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【Objective】 To determine the ELISA kit for screening convalescence plasma with high potency of SARS-CoV-2 IgG by comparing and analyzing the plasma detection results of convalescent plasma collected in different periods via ELISA kits from two manufacturers and the results of mixed plasma with different potency via pseudovirus neutralization experiments. 【Methods】 Two ELISA kits from different manufacturers(named A, B) were used to detect the plasma of 269 convalescent patients collected from Feb.2020~Jan.2022. The correlation and concordance rate of the two results were analyzed to determine the kit preliminarily. According to the titers of diluted series of standard of the preliminary selected kit, 5 mixed plasma samples (G4-G128) with different potency were prepared. The correlation of ELISA IgG results of product A/B, as well as the pseudovirus neutralization test of the original strain, Omicron mutant BA.1 and BA.2 strains were analyzed. Combined with the outside-well dilution mode of the strongly positive samples, the kit for high potency of SARS-CoV-2 IgG screening was determined. 【Results】 When the internal control reference B2 was used as the standard, the detection sensitivity of product A and B was 1∶32 vs 1∶8; the detection sensitivity of product A was 4 times that of product B. The correlation Pearson r between the results given by two kits was 0.944 1(P<0.000 1). Product B with low sensitivity was primarily selected as an alternative kit. The ELISA IgG results of samples from mixed plasma showed that the order of correlation r between product A and B was 0.988. The correlation r between product A and neutralization antibody potency of the three viruses was original strain (0.978)>BA.2(0.970)>BA.1(0.799); the order of correlation r between ELISA IgG results of product B and neutralization antibody potency of the three viruses was original strain(0.994)>BA.2(0.968)>BA.1(0.804). If twice-diluted B2 was taken as the excellent standard, 55.4% of product B met the criterion, while 47.2% of product A met.For positive plasma with high IgG potency, the product B kit required a lower dilution of the sample, which was more convenient to operate. 【Conclusion】 Both of the ELISA IgG kit from product A and B can be used to screen IgG antibodies of SARS-CoV-2, while product B is more suitable for screening positive plasma with high IgG potency.
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【Objective】 To analyze the changes in antibody titer of voluntary blood donors after receiving the COVID-19 vaccine, so as to provide reference for blood donation strategy, follow-up vaccine development and COVID-19 prevention and treatment for healthy people. 【Methods】 1) The serum from voluntary blood donors 2, 4, 8, 12, 16 and 20 weeks after inoculation with two-shot vaccines (inactivated vaccine or recombinant protein vaccine) was collected, and SARS-CoV-2 total antibody (IgG+ IgM+ IgA) detection (colloidal gold method) and neutralizing antibody detection (UPT immunoluminescence method) were conducted. 2) The obtained data were grouped according to collection time, age and gender, and differences between groups were analyzed by t test and ANOVA using SPSS 2.0 statistical software to clarify the trend of total antibodies and neutralizing antibodies. 【Results】 Neutralizing antibodies and total antibodies (IgG+ IgM+ IgA) from voluntary blood donors vaccinated inactivated vaccine or recombinant vaccine had the same trend of change, both reached their peak at the 2nd and 4th week, respectively, after inoculation, and then decreased gradually. The antibody produced by the recombinant protein vaccine had a higher titer than that from inactivated vaccine, and had slower decline and more lasting protection. The neutralizing antibody and total antibody (IgG+ IgM+ IgA) from different genders and ages were not statistically different. 【Conclusion】 Neutralizing antibodies reached its peak in the second week after vaccination, and total antibody titer reached its peak in the fourth week; both were independent of age and gender. After receiving the vaccine, voluntary blood donors should follow the latest instructions on blood donation intervals issued by the government.
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【Objective】 To investigate the trend of neutralizing antibody level in plasma donors who received the 3rd shot of inactivated novel coronavirus vaccine. 【Methods】 Three commercial ELISA kits for novel coronavirus neutralization antibody detection, manufactured by Company A, B and C, were chosen and screened by Pseudotype Neutralization Test from December 2021 to June 2022. A total of 410 plasma samples from 64 plasma donors who received the 3rd shot of inactivated novel coronavirus vaccine and there after donated plasma within six months were detected by the selected ELISA kit from July to October, 2022. The data were analyzed by Excel 2013 and SPSS 26 software. 【Results】 The high-throughput ELISA kit for SARS-CoV-2 neutralizing antibody detection, manufactured by Company A, was selected for further antibody titer detection. The mixed plasma titers were 1 337.34, 1 148.89, 852.19, 681.38, 556.44 and 457.19 U/mL from 1 to 6 months, respectively, after the 3rd shot of vaccine. The neutralizing antibody titer level began to increase around 7 days after the 3rd shot of vaccine injection and peaked (peak range: 264.07-2 208.39 U/mL, median: 569.34 U/mL) at 1 month (range: 9-43 days, median: 22 days), and then gradually decreased (P<0.05). 【Conclusion】 The neutralizing antibody titer of plasma donors who received the 3rd shot of inactivated novel coronavirus vaccine began to rise around 7 days after vaccination, which reached the peak value at around 1 month and then gradually decreased.
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【Objective】 To determine the best collection time period of plasma which can be used for human COVID-19 immunoglobulin for intravenous injection through SARS-CoV-2-IgG change and neutralizing antibody distribution against different virus strain in representative mixed plasma before and after Omicron strain infection by ELISA and pseudovirus neutralization test. 【Methods】 An ELISA method for quantitative detection of SARS-CoV-2-IgG was established and its linear range,accuracy and precision was verified. SARS-CoV-2-IgG potency was detected in 25 convalescent plasma which were collected 20-40 days after confirmed Omicron infection, two groups of mixed plasma samples WP1 and WP2 were prepared according to the SARS-CoV-2-IgG results, and pseudovirus neutralization experiments with different virus strain (prototype strain, BA. 1,BA.2, BA.4/5, BF.7, BQ.1.1) were carried out to determine the distribution of neutralizing antibodies against different virus strain. SARS-CoV-2-IgG potency of representative mixed plasma collected from 14 plasma stations subordinate to the company before and after Omicron strain infection was detected, including Omicron convalescent plasma (OP) collected from different plasma stations from December 2022 to May 2023 and normal pool plasma (VN) feed in March 2023 which collected from March 2022 to December 2022. According to the results, the difference and the change rule with time of SARS-CoV-2-IgG before and after Omicron strain infection were analyzed. 【Results】 The linearity of SARS-CoV-2-IgG ranged from 6.25 to 200 EIU/mL, the accuracy in-batch ranged from 81.793% to 106.985%, the precision in-batch ranged from 1. 100% to 13.000%, and the total error in-batch ranged from 2.988% to 22.679%. The accuracy between batches ranged from 90.788%to 96.893%, the precision between batches ranged from 4.870% to 6.272%, and the total error between batches ranged from 9.192% to 15.399%. The results of pseudovirus neutralizing antibody showed that the potency of different virus strain neutralizing antibodies were in the order of prototype strain>BA.2>BA.4/5>BF.7≈ BQ.1.1>BA.1 and the correlation between WP1 and WP2 was high (Pearson r=0. 931 1, P=0.002 3) which indicated that the potency distribution of neutralizing antibodies of different virus strain in Omicron convalescent plasma was basically stable. Compared with the mixed convalescent plasma sample G128 collected in June 2022, the potency of Omicron neutralizing antibodies of WP series were significantly higher, the ratio of BA.2 antibody to prototype antibody increased from 26.9% (before infection) to 82.6%-87.5% (after infection). The results of VN series before Omicron infection were < 100 EIU/mL, and the results of OP series after Omicron infection showed that the plasma collected from the beginning of December 2022 was the peak of antibody in the same month,and then dropped sharply, entering a short plateau in February-March 2023 (potency was about 40% of the peak value),and then dropped sharply again in April (potency was about 20% of the peak value). 【Conclusion】 The potency and proportion of neutralizing antibody against Omicron subtype in convalescent plasma after COVID-19 Omicron strain infection increased significantly. IgG antibody of plasma donors in different regions reached its peak in the month of infection, then continued to dropped sharply. The best collection period of plasma that can be used for human COVID-19 immunoglobulin for intravenous injection was 1 to 2 months after infection.
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【Objective】 To study the relationship between the plasma IgG, IgM, neutralizing antibody titer and sex, age, collection interval in convalescent patients with COVID-19, so as to guide the plasma collection of convalescent patients with COVID-19. 【Methods】 COVID-19 convalescent plasma was collected to determine the antibody titer, and the difference and correlation of data in each group were analyzed by SPSS statistical analysis software. 【Results】 The median titers (AU/mL)of IgG, IgM and neutralizing antibodies in males and females were 484.24 vs 516.04, 2.13 vs 1.73, and 1 124.74 vs 1 143.99, respectively, and there was no significant difference(P>0.05) . Age had weak positive correlation with IgG and neutralizing antibody, and the Spearman correlation coefficient was 0.188 (P<0.05). The median titers (AU/mL) of IgG, IgM and neutralizing antibody at first donation of 30 repeated donors were 522.3, 2.64 and 1 174.6, respectively, but at second donation were 332.08, 0.63 and 708.96, showing significant difference (P<0.05). 【Conclusion】 There was no significant difference in the plasma IgG, IgM and neutralizing antibody titers in convalescent COVID-19 patients of different ages and genders, and the titers met the requirements of clinical treatment guidelines. Although the plasma antibody level of repeated donors has decreased, it still has clinical value.
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【Objective】 To analyze the results of different methods for reactive samples screened by the enzyme linked immunosorbent assay (ELISA) against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in blood donors. 【Methods】 From March to April 2020, a total of 8 632 blood samples in Shenzhen were screened for SARS-CoV-2 total antibodies (TAb, including IgG, IgM, IgA) in plasma using ELISA(PC group), the antibody reactivity samples and their follow up plasma samples (FC group), and samples of disease control group(DC group) from January to April 2020 were detected using the following methods: 1) ELISA method for detecting IgG, IgM, and (or without detection) TAb; 2) pseudovirus neutralizing antibody test(pVNT); 3) western blot (WB) of SARS-CoV-2 antibody. The negative control group(NC group) from February to April 2020 performed ELISA and WB testing. 【Results】 Among the 34 total antibody positive samples, 2 were positive for pVNT test, and the total antibody, IgG and WB in the initial screening and tracking testing were positive. Thereafter, it was determined to be confirmed positive. The other 2 cases were positive for pVNT test, while the samples with positive WB results were in the follow-up stage. The TAb, IgG, and pVNT results did not conform to the dynamic evolution of antibodies, and cannot be determined as confirmed positive. 【Conclusion】 The infection status of antibody reactivity samples screened by SARS-CoV-2 ELISA can be judged by the logic of pVNT, WB and the dynamic change of antibody.
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ObjectiveTo determine the difference of serum neutralizing antibody levels in healthy persons following the vaccination of inactivated SARS-CoV-2 vaccines. MethodsHealth care workers that received inactivated SARS-CoV-2 vaccines were enrolled in Sichuan provincial people's hospital from January to December 2021. All participants were classified into four groups according to the number and time of vaccination， which were groups of 28 days after the second dose， 180 days after the second dose， 28 days after the third dose and 150 days after the third dose. Serum neutralizing antibody was quantitatively detected by chemiluminescence method. Furthermore， the serum neutralizing antibody levels were compared within and between groups by gender， age and body mass index（BMI）. ResultsA total of 349 participants were enrolled in this study， including 113 males and 236 females. The positive rates of neutralizing antibody in the groups of 28 days after the second dose， 180 days after the second dose， 28 days after the third dose and 150 days after the third dose were 74.0%， 25.7%， 100.0% and 100.0%， respectively. In the four groups， neutralizing antibody levels were 10.38 （5.76， 24.00） AU·mL-1， 4.18 （3.00， 6.18） AU·mL-1， 41.18 （25.80， 116.21） AU·mL-1 and 33.33 （18.09， 69.12） AU·mL-1， respectively. The positive rate of neutralizing antibody significantly differed across the groups （P<0.001）. Furthermore， neutralizing antibody level in the third dose groups were significantly higher than that in the second dose groups （P<0.001）. Neutralization antibody level in young people （<45 years old） was significantly higher than that in middle-aged and elderly people （≥45 years old） in the groups of 180 days after the second dose and 28 days after the third dose （P<0.05）. Additionally， neutralization antibody level in normal weight participants was significantly higher than that in overweight and obese participants in the group of 28 days after the second dose （P<0.05）. However， no significant difference was found in all groups by gender （P>0.05）. ConclusionCompared with two doses of inactivated SARS-CoV-2 vaccine， three doses can significantly induce higher neutralizing antibody and stronger immune protection. Age and BMI have certain effect on the neutralizing antibody.
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@#Objective To prepare the second generation internal control reference(B2)for Ig G antibody against severe acute respiratory symptom coronavirus 2(SARS-CoV-2)and evaluate its applicability in ELISA detection method. Methods Among the volunteers vaccinated with SARS-CoV-2 inactivated vaccine(BBIBP-Cor V)produced by Beijing Institute of Biological Products Co.,Ltd.,19 Ig G antibody positive plasma samples with ELISA-Ig G dilution ratio of 20 ～ 60 were screened,and the Ig G antibody,IgM antibody and neutralizing antibody were detected by ELISA,B2 was prepared from nonlipid plasma with ELISA-Ig G dilution ratio of 32 ～ 45,IgM negative and similar neutralizing antibody inhibition rate. The neutralizing antibody potency of the first generation internal control reference(B1)and B2 detected by ELISA was calibrated with the first generation WHO international standard of anti-SARS-CoV-2 immunoglobulin(NIBSC 20/136),and the accelerated stability(storage at 2 ～ 8 ℃ for 5,8,14,20,and 30 d respectively),the service stability(storage at 18 ～25 ℃ for 1,2,and 3 h respectively),the freeze-thaw stability(1,2 and 3 times)and the long-term stability(storage at-25 ℃ for10 months)of B2 were tested. B2 was used as standard to detect plasma after single vaccine immunization and mixed plasma was prepared according to different ELISA-Ig G dilution ratio. The correlation and linear regression analysis between ELISA-Ig G dilution ratio and neutralizing antibody potency of pseudovirus in mixed plasma were carried out. Results Among 19 plasma samples,5 samples were non-lipid plasma with ELISA-Ig G dilution ratio of 32 ～ 45,IgM negative and similar neutralizing antibody inhibition rate. B2 was prepared by mixing every plasma in equal volume fraction,and the dilution ratio of ELISA-Ig G was assigned to 32. The neutralizing antibody potency of B1 calibrated with NIBSC 20/136 was 133. 38 EIU/m L and that of B2 was 122. 14 EIU/m L. The recovery rates of accelerated stability,service stability,freeze-thaw stability and long-term stability of B2 were all in the range of(100 ± 15)%. The ELISA-Ig G dilution ratio of the mixed plasma from the same source was significantly correlated with the neutralizing antibody potency of pseudovirus.(each R~2> 0. 99,each P < 0. 000 1).Conclusion B2 prepared from plasma immunized with SARS-CoV-2 inactivated vaccine can replace B1 prepared from plasma of COVID-19 convalescent patients.
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@#Objective To analyze the correlation of different methods for the detection of antibody titer after immunization with severe acute respiratory symptom corona virus 2(SARS-CoV-2) vaccine,and provide a methodological basis for the specific antibody detection.Methods The seroconversion rate of IgG antibody and neutralizing antibody titer of SARS-CoV-2 inactivated vaccine clinical trial serum samples were detected by micro-cell neutralization assay and three ELISA methods(using S protein,N protein and inactivated whole virus particles as antigens respectively),and the correlation among the methods was analyzed.Results The seroconversion rates detected by neutralizing antibody,S antibody,N antibody and whole virus antibody were 84.3%,91.3%,65.2% and 46.6%,and the geometric mean titers were 16.6,945.9,72.7 and 18.8,respectively.The correlation coefficients(r) between the results of three ELISA methods(using S protein,N protein and inactivated whole virus particles as antigens) and micro-cell neutralization assay were 0.494,0.371 and 0.181respectively.Conclusion Detection of SARS-CoV-2 S antibody level reflected the activation of the humoral immune response characterized by elevated antibody level to a great extent.
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Since an outbreak of coronavirus disease 2019, there have been more than 664 million confirmed cases and more than 6.7 million deaths worldwide.The Omicron variant discovered in November 2021 has become a dominant variant in China.Compared with the general population, Omicron infection mainly presents short-term upper respiratory symptoms followed by quick recovery; solid organ transplant recipients have the characteristics of a high incidence of severe disease and high mortality after infection, and the incidence of secondary infection and rebound positivity is significantly higher than that of the general population.This review focused upon preventive strategies of solid organ transplant recipients from the perspectives of the characteristics of organ transplant recipients, general preventive strategies, vaccination and long-acting neutralizing antibodies.
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@#Abstract: Objective To construct SARS-CoV-2 receptor binding domain molecular probe for monoclonal memory B cell sorting and obtain RBD specific neutralizing antibodies from peripheral blood mononuclear cells (PBMCs) of COVID-19 convalescents by single-cell sorting. Methods The SARS-CoV-2 RBD sequence was downloaded from GenBank, and the Avi tag and 6-histidine tags were added at the C-terminal. After codon optimization, it was chemically synthesized, cloned into the pDRVI1.0 vector, expressed after transfection of 293F cells, and biotinylated consequently. RBD-specific B cells were sorted out with this probe1 from the PBMCs of convalescents recovered from COVID-19. After B cells were lysed, the variable regions of heavy chain and light chain were amplified, cloned into the antibody expression vector, and transfected into 293F cells to express the antibody. Then the antibody was purified from the supernatant using protein A column and SARS-CoV-2 pseudovirus was used to test their neutralizing activity. Results RBD-Avi probe was produced and successfully biotinylated sequentially with an efficiency of 30%-50%. Western blot analysis revealed that the biotinylated probe was recognized by the antibodies purified from COVID-19 convalescent plasma. Using this probe, 7 and 16 RBD-specific memory B cells were successfully isolated from the PBMCs of two convalescent individuals, accounting for 0.24% and 0.17% of the total cell population, respectively. After amplifying the variable regions of antibody heavy and light chains from the lysed B cells, 7 and 12 pairs of antibody heavy-light chains were obtained. A total of 16 antibodies were expressed in the convalescent individuals, and most of the purified antibodies showed neutralizing activity against the pseudovirus, with IC50 values of 6 antibodies below 1 μg/mL. The IC50 values of XJ-A9 and SCF-F1 against the wild-type pseudovirus were 0.07 μg/mL and 0.35 μg/mL, respectively. Conclusion The SARS-CoV-2 RBD molecular probe constructed in this study has good antigenicity, and the isolated antibodies present neutralizing activity against wild-type SARS-CoV-2 pseudovirus.
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@#ObjectiveTo develop and apply a method for detecting the titer of varicella-zoster virus(VZV)neutralizing antibodies based on complement dependence,so as to improve the sensitivity of traditional plaque reduction neutralization assay for detection of the titer of VZV antibody.MethodsThe antigen(live attenuated varicella vaccine)and antibody(human VZV immunoglobulin)were mixed in different proportions and different incubation times. After neutralization,the antigen-antibody mixture was inoculated into human diploid cell 2BS strain cultured in a six-well plate. After 7 ～ 10 d of culture,the number of plaques was counted by Coomassie brilliant blue staining,and the 50% neutralizing antibody titer was calculated by Karber′s formula. Under the optimal neutralization conditions obtained,the effect of complement on the sensitivity of neutralization experiment was explored by changing the addition amount of complement(lyophilized guinea pig serum)to evaluate the optimal addition amount of complement. According to the determined neutralization test parameters,the neutralizing antibody titers of 12 anti-VZV mouse sera and 14 anti-VZV human sera were detected by using traditional plaque method and complement-dependent plaque method respectively.ResultsThe key parameters of the detection method were determined:the titer of VZV standard antigen was 500 ～ 1 000 PFU/mL;the proportion of complement added to the antigen-antibody neutralization system was 1∶10(v/v),and the neutralization condition was 37 ℃ for 1 h. Both the complement-dependent plaque method and the traditional plaque method were positive for anti-VZV mouse serum antibody,while the antibody titer detected by the traditional plaque method was generally lower,and the antibody level of mice inoculated with 2 doses of live attenuated varicella vaccine was significantly higher than that of mice inoculated with 1 dose(t = 0. 45,P < 0. 05);Both of the two methods were positive for anti-VZV human serum antibody.ConclusionA complement-dependent detection method for neutralizing antibody titer of VZV was established. The addition of complement significantly improved the sensitivity of neutralization detection. The evaluation of the titers of neutralizing antibodies in mouse serum with different immunization strategies by the method suggested that the immune effect of two doses of vaccine was better than that of one dose.
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Objective@#To investigate the seroprevalence and influencing factors of serum neutralizing antibodies among SARS-CoV-2 infected individuals, so as to provide the evidence for developing the health management and COVID-19 vaccination strategy among SARS-CoV-2 infected individuals.@*Methods@#Recovered SARS-CoV-2 infected individuals from January 1st, 2020 to February 10th, 2021 in Zhejiang Province were recruited in March 2021. Participants' demographics, underlying diseases, date of definitive diagnosis and severity of clinical symptoms were collected using questionnaire surveys, and serum neutralizing antibody against SARS-CoV-2 was detected using a fluorescent immunoassay. In addition, factors affecting the seropositivity of neutralizing antibody against SARS-CoV-2 were identified using a multivariable logistic regression model. @*Results@#A total of 559 SARS-CoV-2 infected individuals were enrolled, including 480 confirmed cases and 79 asymptomatic carriers, with an median (interquartile range) age of 47.00 (22.00) years, and all participants had never received COVID-19 vaccination. The median (interquartile range) duration from diagnosis to serum sampling was 387.00 (11.00) days, and the seroprevalence of neutralizing antibody against SARS-CoV-2 was 83.90%. The serum neutralizing antibody against SARS-CoV-2 was all positive 9 months after diagnosis, and the seroprevalence of neutralizing antibody against SARS-CoV-2 appeared no tendency towards a decline with time within 14 months after diagnosis (P>0.05). Multivariable logistic regression analysis showed that women were 1.892 times (95%CI: 1.169-3.064) more likely to produce serum neutralizing antibodies against SARS-CoV-2 than men, and mild, common and severe/critically ill SARS-CoV-2 infected cases were 2.438 (95%CI: 1.305-4.557), 4.481 (95%CI: 2.318-8.663), and 23.525 (95%CI: 2.990-185.068) times more likely to produce serum neutralizing antibodies against SARS-CoV-2 than asymptomatic carrier, respectively.@*Conclusions@#The seroprevalence of neutralizing antibody was 100.00% among SARS-CoV-2 infected individuals within 9 months after diagnosis. Individuals' gender and severity of clinical symptoms correlate with the seroprevalence of neutralizing antibody against SARS-CoV-2.
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Background & objectives: The pandemic caused by the SARS-CoV-2 has been a threat to humankind due to the rapid spread of infection and appearance of multiple new variants. In the present study, we report the dynamics and persistence of immunoglobulin G (IgG) and immunoglobulin M (IgM) antibodies in asymptomatic and symptomatic COVID-19 patients by chemiluminescent assay. Methods: A total of 463 serum samples from 218 SARS-CoV-2 PCR-positive patients were collected over a period of 124 days post-onset of disease (POD). Antibody levels were measured by chemiluminescence bioanalyzer. Neutralizing antibody titres were assessed by plaque reduction neutralization test (PRNT) for SARS-CoV-2. Results: Both IgM and IgG started appearing from day five post-infection in symptomatic and asymptomatic patients. IgM antibody response peaked around day 35 POD and rapidly diminished thereafter, with the last IgM-positive sample observed at 90 days POD. IgG antibody response peaked around 45 days POD and persisted till 124 days. The chemiluminescence immunoassay (CLIA) results showed a moderate correlation (R=0.5846, P<0.001) compared with PRNT. Additional analysis indicated a neutralizing titre of 250 corresponded to 12.948 AU/ml of YHLO iFlash SARS-CoV-2 IgG units. Interpretation & conclusions: Both symptomatic and asymptomatic COVID-19 patients seem to initiate production of antibody responses from day five of onset of disease. Although the CLIA gives high sensitivity and specificity and also its binding IgG antibody titres may correlate moderately with protective immunity, our results indicate that the values of binding antibody alone may not be a perfect guide to represent virus neutralization titre during donor selection for plasma therapy. However, IgM and IgG antibody detection may help in monitoring the status of disease progression and burden in the community.
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Background & objectives: During the COVID-19 pandemic it was important to assess the antibody profile in individuals vaccinated with Covaxin (BBV152) and Covishield (ChAdOx1 nCoV-19) with both 28 and 84 days gaps between two doses, those infected with SARS-CoV-2 and post-COVID-19-infected individuals vaccinated with only one dose of either of the vaccines. The present study was aimed to assess these objectives. Methods: Fifty real time reverse transcription–polymerase chain reaction (qRT-PCR)-confirmed COVID-19-infected individuals, along with 90 COVID-19-naïve (BBV152 and ChAdOx1 nCov-19)–vaccinated individuals, were included in the study. Individuals who received a single dose of either vaccine with a confirmed past diagnosis of SARS-CoV-2 infection (n=15) were also included. Blood samples were collected strictly between the 4th and 5th wk after development of symptoms for SARS-CoV-2 infected individuals and after the first/second vaccination dose. Antibody profile assessment was done using whole-virus, spike-receptor binding domain (RBD) and nucleocapsid-specific ELISA kits along with neutralizing antibody kit. Results: There was an overall 97.7 per cent seropositivity rate in vaccinated individuals, and a strong correlation (R2=0.8, P<0.001) between neutralizing and spike-RBD antibodies. Among individuals who received two standard doses of ChAdOx1 nCoV-19 vaccine, the spike antibody levels developed were of higher titre with a longer prime boost interval than in those with shorter intervals (P<0.01). Individuals vaccinated with two doses as well as only one dose post-SARS-CoV-2 infection had high neutralizing and spike-specific antibodies. Interpretation & conclusions: High neutralizing and spike-specific antibodies were developed in individuals vaccinated only with one dose of either vaccine post-SARS-CoV-2 infection. With the main priority being vaccinating majority of the population in our country, single-dose administration to such individuals would be a sensible way to make the most of the limited supplies. Furthermore, neutralizing antibody levels observed in COVID-19-naïve vaccinees imply the need for booster vaccination.
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【Objective】 To detect the anti-SARS-CoV-2 neutralizing antibody levels in convalescent plasma (CP) and to evaluate whether it has specific anti-SARS-CoV-2 S antigen effect, so as to provide laboratory data support for clinical use of CP. 【Methods】 Nine CP donors who have recovered from COVID-19 were studied, and 4 volunteers who completed the vaccination and 3 asymptomatic infected blood donors were compared. Anti-SARS-CoV-2 antibodies including total antibody, IgM and IgG were measured by chemiluminescence microparticle immunoassays (CMIA) test in three groups. The VSV pseudovirus-based neutralization assay for evaluating neutralizing antibodies against SARS-CoV-2 was carried out in all samples. 【Results】 All samples were tested positive by the total antibody and IgG CMIA in COVID-19 CP donors and recipients of inactivated COVID-19 vaccine. High titers of IgG were observed in CP donors and vaccine recipients compared with asymptomatic blood donors. All vaccine recipients and 8 of 9 CP donors tested positive by SARS-CoV-2 pseudovirus-based neutralization test, whereas all asymptomatic blood donors tested negative. 【Conclusion】 The levels and characteristics of neutralizing antibodies among COVID-19 CP donors, vaccine recipients and asymptomatic blood donors were different. When unable to implement the pseudovirus assay to measure neutralizing antibodies, the detection of total antibody can be considered instead.
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【Objective】 To investigate the distribution of plasma donors with high titer neutralizing antibodies against human cytomegalovirus (HCMV) in the general plasma donor population. 【Methods】 920 plasma samples of Taibang were tested in April 2014 to investigate the distribution of anti-HCMV neutralizing antibodies. After further testing of mixed plasma, the threshold for screening plasma was determined. From October 2019 to May 2020, neutralizing anti-HCMV in 40 078 plasma samples from 11 plasma stations in Shandong province were screened by the microcytopathic method (modified high-flux neutralization test method). The proportion of neutralizing anti-HCMV enriched in high titer and the distribution in the donor population were analyzed by SPSS 26 and Minitab19 analysis software. 【Results】 Among 920 samples, 73.26%, 0.43%, and 8.69% of them had neutralization titer<1∶15, ≥1∶60 and ≥1∶30, respectively. The neutralization titer of mixed plasma was detected, and 1∶30 was determined as the high titer. The yielding rate of high titer neutralizing anti-HCMV in Shandong was 9.06% (3 633/40 078). The proportion of plasma donors with high-titer neutralizing anti-HCMV in the donation population from plasma stations was 4.95%~13.03% (9.06±2.07) %. The proportion of plasma donors with high-titer neutralizing anti-HCMV by gender was 15.67% (2 185/13 951) in women and 5.54% (1 448/26 127) in men(P<0.05). 【Conclusion】 There was a certain proportion of plasma donors wiht high titer neutralizing anti-HCMV in the population of plasma donors in Shandong, and they can constantly serve neutralizing anti-HCMV to ensure the production of anti-HCMV immunoglobulin preparations.